Determination of Optimum Phosphorus Rate for Tef (<i>Eragrostis tef/Zucc./Trotter</i>) Under Balanced Fertilization in Vertisol, East Shoa Zone, Oromia Riginal State, Ethiopia

Abstract

The fertilizer requirement of tef varies from agro-ecology to agro-ecology and from soil to soil. Therefore, the objective of this study was to refine optimum phosphorus rate for tef under balanced fertilization. The experiment was conducted on-farm during main cropping season for two consecutive years (2015-2016) in Vertisol at Ada’a District. The experiment had 8 treatments (six phosphorus rates each with fixed amount of N, K₂O, S, Zn and B, negative control (without fertilizer), and recommended NP (60 N+10 P) kg ha^-1). Phosphorus was applied at the rates of 0, 23, 46, 69, 92 and 115 kg P₂O₅ ha^-1 using TSP (triple super phosphate) as a source of it. Nitrogen, K₂O, S, Zn and B were applied at the rate of 92, 90, 30, 2 and 1 kg ha^-1 from urea, potassium chloride, calcium sulfate, zinc sulfate and borax penta hydrate fertilizers, respectively. The experiment was laid out in a randomized complete block design (RCBD) with triple replication of each treatment. The ANOVA revealed that plant height and number of tillers were highly significantly affected (P<0.05) with phosphorus application rates. The above ground biomass (AGB), grain yield (GY) and straw yield (SY) which received phosphorus rates strongly significantly affected (P<0.001) over control. The maximum grain yield was recorded at 69 kg P₂O₅ ha^-1(30 kg P ha^-1) following by 46 kg P₂O₅ ha^-1 (20 kg P ha^-1) and the results were found being 1719 and 1607 kg ha^-1, respectively. Similarly, the maximum net benefits was recorded at 69 kg P₂O₅ ha^-1 (30 kg P ha^-1) and then at 46 kg P₂O₅ ha^-1 (20 kg P ha^-1) and the amounts were found being 56035.1 and 54744.4 ETB ha^-1, respectively. However, the maximum marginal rate of return was recorded at 46 kg P₂O₅ ha^-1 (20 kg P ha^-1) and then by recommended NP with MRR 1329.5% and 306.8%, respectively. Therefore, 46 kg P₂O₅ ha^-1 (20 kg P ha^-1) could be recommended for the study site and areas having similar agro-ecology with the study area.